1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image using an electrophotographic method. In particular, the present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction peripheral including the aforementioned plurality of functions.
2. Description of the Related Art
Conventionally, an image forming apparatus using an electrophotographic method generally includes a drum-shaped photosensitive member 1 as an image bearing member as illustrated in FIG. 1. In such an image forming apparatus, a charger 2 uniformly charges a surface of the photosensitive member 1, and an exposure device 3 exposes the charged photosensitive member 1 according to image information. Consequently, an electrostatic image is formed on the photosensitive member 1. The electrostatic image is then visualized by toner in a developer using a developing device 4 and thus becomes a toner image. A transfer device 5 transfers the visualized toner image to a recording material S, and a fixing device 6 fuses and fixes the toner image on the recording material S by applying heat and pressing force.
After the above-described transferring process is performed, a cleaning device 7 removes residual toner on the photosensitive member 1. Further, a neutralization device 8 removes any remaining charge on the photosensitive member 1 to prepare for the next image forming process.
The developing device 4 can use a two-component developer including non-magnetic toner particles (toner) and magnetic carrier particles (carrier). Since the two-component developer does not have to include a magnetic substance in the toner, a favorable color can be acquired. Consequently, the two-component developer is widely-used particularly in a color image forming apparatus.
An example of a general configuration of the developing device 4 using a two-component developer is illustrated in FIGS. 3 and 4.
Referring to FIGS. 3 and 4, the developing device 4 includes a developer container 41 that contains the developer. The developer container 41 is divided into a developing chamber (developer conveyance path) 41a and an agitating chamber (developer conveyance path) 41b by a partition wall 41c that is extended in a perpendicular direction.
A first developer convey agitating member 42 and a second developer convey agitating member 43 are formed in the developing chamber 41a and the agitating chamber 41b respectively. Further, transferring portions (developer conveyance paths) 41d and 41e are formed at edges of the partition wall 41c in a longitudinal direction to allow the developer to pass between the developing chamber 41a and the agitating member 41b. The first and second developer convey agitating members 42 and 43 agitate and convey the developer, so that the developer is circulated inside the developer container 41. A developing sleeve 44 as a developer bearing member is rotatably disposed at a position facing the photosensitive member 1. A magnet 45 as a magnetic field generation unit is fixedly disposed inside the developing sleeve 44.
The magnet 45 in the developing device 4 includes 3 or more poles. The developer agitated by the first developer convey agitating member 42 is attracted by a magnetic force of a convey magnetic pole N2 (lift pole) for lifting the developer. The developer is then conveyed to a developer reservoir portion 48 by rotation of the developing sleeve 44. The amount of the developer is regulated by a developer back member 47. Further, the developer is sufficiently attracted by a convey magnetic pole (cut pole) S2 having a predetermined magnetic flux density or more to stably attract an amount of developer, and conveyed while forming a magnetic brush.
A regulating blade 46 that regulates a layer thickness of the developer cuts the tip of the magnetic brush to make a developer amount appropriate. The convey magnetic pole N1 then conveys the developer to a position facing the photosensitive member 1, and the developer is supplied for development in a developing pole S1. At the position facing the photosensitive member 1, only the toner is transferred to an electrostatic image formed on the surface of the photosensitive member 1 by a developing bias applied on the developing sleeve 44. As a result, a toner image is formed on the surface of the photosensitive member 1 according to the electrostatic image.
In the above-described image forming apparatus, if a foreign substance is caught between the developing sleeve 44 and the regulating blade 46, a developer coat becomes thin in the region where the foreign substance is caught. Consequently, the density of the developer becomes thin.
To solve such a problem, Japanese Patent Application Laid-Open No. 11-231645 discusses a method of removing the foreign substance that is caught between the developing sleeve 44 and the regulating blade 46 by installing a member that vibrates the regulating blade 46 itself.
However, a problem arises in a case where the method discussed in Japanese Patent Application Laid-Open No. 11-231645 is applied to an image forming apparatus which includes a plurality of developing devices that each develops images on a plurality of drums. That is, if the vibration member which vibrates the regulating blade of each developing device is simultaneously vibrated, noises produced due to vibration can be overlapped, so that very loud noise is generated.